I just got one of he shines new HyperPixel Round screens and got in a bit of a pickle getting other I2C devices working with it! Took me quite a while, a load of googling and eventually buzzing the pins on the screen itself to realise that the HyperPixel install scripts disable the standard I2C pins and you need to use GPIO 10 and 11.
This is explained at the bottom of the original HyperPixel4 guide: Getting Started with HyperPixel 4.0 - Pimoroni Yarr-niversity but that’s not linked to on the HyperPixel 4 Square or 2.1 Round product pages (as far as I can see).
Would be a great help if the I2C pin changes are explicitly mentioned on all the HyperPixel product pages, I don’t consider myself a n00b, but it took me way longer than it should have to find the issue and resolve it!
Hope this thread helps others that have I2C issues!